Singapore Airlines KrisFlyer - Booking class Question

I'm trying to book a one-way NRT-LAX in economy. But I lost the cheaper fares while still trying to finalize my itinerary. The booking class closer to the date I want to travel are more expensive in classes B, Y and S. The cheapest E fare is a few days earlier. If I book it now and later change for a later date, will I be charged the difference?
Thanks.

I'm trying to book a one-way NRT-LAX in economy. But I lost the cheaper fares while still trying to finalize my itinerary. The booking class closer to the date I want to travel are more expensive in classes B, Y and S. The cheapest E fare is a few days earlier. If I book it now and later change for a later date, will I be charged the difference?
Thanks.

If you booked on E, and rebooked on later date then obviously no fare difference if E clears.If your booked on E, rebooked on the date you want and still no E , but only Y, S, then obviously theres a fare difference between those booking classes.So, my advise, book now on E on that earlier date, then waitlist on your desired date, call them to put you first on the list so that when E clears on that date, you can fly on the date you want while saving money on this ridiculous airline fare structures.